Photographic tracing cloth



y 1944- G. F. NADEAU ET AL 1 PHOTOGRAPHIC TRACING CLOTH Filed July 30', 1942' 1s MULS/ON. I 1. mo N/TRATE. U [/3 EL AND NITRATE 0/2 RESIN. 10 0, CLOTH IMPREGNATED WITH WAX AND MINERAL OIL.

AND N/TRATE 0R RES/N. ELLULOSE ACETATE ANTI-CURL LAYER.

Ga/e E Naaeau WM BY Patented May 30; 1944 UNITED STATES PATENT OFFICE PHOTOGRAPH? TBACING CLOTH Gale r. Nllleall and Clemens 1;. Starch, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester Jersey N. Y., a corporation of New Application July 30, 1942, Serial No. 452,878

5 Claims. This invention relates to photographic tracing cloth and particularly to' tracing cloth having increased transparency and flexibility.

transparency is a result of the waterproofing solution of some of the wax and oil originally incorporated in the cloth for the purpose of increasing its transparency.

The transparent qualityof the photosensitive material is of considerable importance, since it determines the rate at which prints can be made. For example, a printing machine using a tracing made on an originally unsensitized tracing cloth medium may operate at approximately 8. feet. per minute. Using the usual waterproofed and sensitized tracing cloth, the transparency of the print may be so reduced that the speed of the machine is only about 6 feet per minute. This means a 25% reduction in the output of the machine, which is a serious curtailment of its value.-

The material prepared according to the present invention would, by comparison, permit a speed of about 10 feet per minute.

.It is, therefore, the object of the present invention to provide a sensitive tracing cloth having improved flexibility and transparency characteristics.

We have found that both transparency and the flexibility of the photosensitive tracing cloth can be improved by the pretreatment of the cloth with certain oils, waxes or plasticizers preliminary to a waterproofing application of a mixtureof gelatin and certain cellulose esters of synthetic resins.

In the accompanying drawing, the single fig-- ure is a sectional viewoi' tracing cloth sensitized according to our invention.

Tracing cloth may be waterproofed, prior to sensitizing, by the application of successive layers of'mixed gelatin and cellulose nitrate, and cellulose nitrate, as described in Nadeau and Couch U. S. Patent 2,117,814, granted May 1'7, 1938. Such sensitized cloth is not entirely satisfactory with respect either to transparency or tofiexibility. v

A simplification of the sensitive tracing cloth described in the Nadeau and Couch U. 3. Patent 2,117,814 may be efiected by increasing the-ratio of nitrate to gelatin in the subbing layer to such extent that it iunctions as a waterproofing layer, thereby permitting elimination oi the nitrate waterproofing layer. Some improvement in transparency is also thereby accomplished. A sensitive tracing cloth of this type is described in Nadeau and Smith U. S. application Serial No. 401.768, flied July 10, 194i.

According to the present invention a marked improvement in transparency and flexib li y of the sensitive cloth is eifected by pretreating the sized cloth with a solution of wax, oil'or plasticizer, or mixture of these, prior to the appiication to both sides of the cloth, of a waterproofing layer of gelatin mixed with a suitable proportion of cellulose ester or synthetic resin. Thiswaterproofing layer is coated with a gelatin and cellulose nitrate sub and a sensitive emulsion layer, and the opposite side of the waterproofed cloth is coated with an anticurl layer, preferably of cellulose acetate.

Our'invention will now bemore specifically described by reference to the-accompanying drawing.

As shown in the drawing, II is a cloth base' such as is customarily used as tracing cloth. It is first treated with a solution of wax, oil, or plasticizer, preferably a mixture of paraflin wax and mineral oil. This material increases the transparency of the cloth.

Waterproofing layers ii of gelatin and. cellulose nitrate or gelatin and synthetic resin are next applied to both sides of the cloth. A layer 'i! of gelatin and cellulose nitrate of different composition than the waterproofing layer II is applied to one of the waterproofing layers. This layer ii acts as a sub for the sensitive emulsion layer i3. The opposite side of the cloth has on it an anticuri layer H, preferably of cellulose acetate, although other suitable materials can be used.

The following example illustrates our preferred method of procedure:

A good grade of commercial tracing cloth is first treated on bothfaces with the following solution:

Per cent Paramn wa 2 Mineral oi 3 Propylene dichloride Following this application, both surfaces of the cloth are coated with the following solution:

Acetic a On the face of the cloth, the waterproof layer is subbed with the following. solution:

Gelatin Cellulose nitrate (3-5 see. viscosity, nitro- Per cent 1.2

gen content 11%) 0.2 Acetic acid 1.0 Water 10.9 Methyl nlonhnl 57, Acetone 30.0 ClCl3.6H2O weight of gelatin A.

To control curl and static, the back of thefilm is coated. with a low viscosity cellulose acetate solution of the following composition:

Per cent Cellulose aceta 6 Methyl Cellosolve Acetone 69 Considerable variation in these coating formulas is possible. For example, the pretreating solution may contain various oils or waxes, or plasticizers, such as triphenyl phosphate, alkyl stearates, Arochlorichlorinated diphenyl), Santicizersn'castor 011; corn oil, sulfonated castor oil. and dibutyl sebacate. The coating solvent for this material may be ethylene dichloride, propylene dichloride, or mixtures of these chlorinated hydrocarbons with butyl alcohol or ligroin, aromatic hydrocarbons, such as benzene and toluene, and commercial solvent mixtures, such as Bayway naphtha.

In the waterproofing layer, the cellulose nitrate may be replaced by other cellulose esters, such as hydrolyzed cellulose acetate or hydrolyzed cellulose acetate propionate, or by synthetic resins such as polyvinylacetate, Santolites, Durez or Arochlor.

The iunction of the wax in this combination is to prevent the oil from exuding from the cloth. The formula in the specific example provides a finished cloth showing freedom from this defect.

To obtain thesame high transparency without the wax would require a solution containing ap proximately 10% oil, which would result in severe bleeding of the oil from the cloth.

An obvious method of applying the oil to the cloth would be to incorporate it in the nitrate solve oils in the waterproofing solution and since any large droplets of oil would render the coat ing hazy, and the finished cloth less transparent, this method of applying the oil is undesirable.

A film manufactured by our preferred method will have, after processing, a light transmission of approximately 70%, where the original cloth had a transmission of about 60%. The finished cloth, without the transparentizing treatment of the present invention would have a transmission of only about 33%. Our method, therefore, not

only prevents a loss in transmission as a result of the waterproofing operation, but actually makes. it possible to increase the transparency of the original stock. g

It will be understood that the examples included herein are illustrative only, and that our invention is to be taken as limited only by the scope of the appended claims.

We claim:

1. The method of making a sensitive tracing cloth of improved transmission and flexibility characterstics which comprises treating a sized cloth with a solution containing approximately 5% of a mixture of a wax and oil transparentizing agent, coating the treated cloth with a solution of gelatin and cellulose ester and thereby depositing a waterproofing layer containing at least cellulose ester, and applying to one side of said waterproofed cloth, a subbing layer and a gelatino-silver halide emulsion layer.

2. The method of making a sensitive tracing cloth of improved transmi sion and flexibility characteristics, which comprises treating a sized clotn with a solution containing approximately 5% of a substantially equal mixture of paramn wax and mineral oil, coating both sides of the treated cloth with a solution of gelatin and cellulose nitrate in the ratio of 1 part gelatin to approximately 7 parts of cellulose nitrate and thereby depositing waterproofing layers on the 'cloth, and applying to one side of said waterproofed cloth, a gelatin and cellulose nitrate subbing layer and a gelatino-silver halide layer.

3. A light-sensitive tracing cloth oi improved transmission and flexibility characteristics, comprising a cloth base transparentized with a solution containing approximately 5% of a mixture of wax and mineral oil, a single waterproofing layer of gelatin and cellulose ester on each side of said base, and a light sensitive layer on one side of said base.

4. A light-sensitive tracing cloth of improved transmission and flexibility characteristics, comprising a cloth base transparentized with a so-' lution containing approximately 5% oi a mixture of'parafiln wax and mineral oil, a single waterproofing layer of gelatin and cellulose ester containing at least 75% cellulose ester, on each side of said base, a subbing layer of gelatin and cellulose ester on one of said waterproofing layers, and a light-sensitive layer on said subbing layer.

5. A light-sensitive tracing cl'oth of improved transmission and flexibility characteristics, comprising a cloth base transparentized with a solution containing approximately 5% of a mixture of parafiin wax and mineral oil, a single waterproofing layer of gelatin and cellulose nitrate in the ratio of 1 part gelatin to approximately 7 parts cellulose nitrate on each side of said base, a subbing layer of gelatin and cellulose nitrate on one of said waterproofing layers, and a gelatinosilver halide emulsion layer on said subbing layer.

GALE F. NADEAU. CLEMENS B. STARCK. 

